For sentimental value: HIV sequence data (and other data) from 1980 till now. Did my thesis on these ;-).

In general, there is an enormous amount of gene sequence data around, not just HIV.

http://www.ncbi.nlm.nih.gov/sites/

Whole genome sequences of eukaryotes (including humans): http://www.ncbi.nlm.nih.gov/genomes/leuks.cgi